Saturday, March 3, 2012

The Human Volcano

One sunny afternoon this week I visited a large commercial nursery in Pennsylvania, located just across the Delaware River from New Jersey. By way of contrast - on another, intermittently cloudy day, I hiked through Jockey Hollow National Park, a bit north of Wit's End, in Morristown.

The pictures in this post are from those two excursions, starting with the drive through the countryside to the grower's location, in a chronological order of progression.

I had been waiting for a pleasant day to make the trip to this nursery, because I think it's important to verify that whatever is killing trees around the world - an increase in the mortality rate that is now well documented by scientific surveys - is not due to localized outbreaks of insects, disease or fungus; nor is it long-term drought from climate change, nor is it even necessarily the depletion of calcium and magnesium in the soils from acid rain (although certainly all those things are occurring, and bad).

But, the shrubs and young trees being grown in nurseries are watered, and the soil is enriched or supplemented with nutrients, and yet they are demonstrably dying off and exhibiting the identical symptoms of damage from air pollution as older trees situated in a wide range of habitats.

My intention all along for the nursery was to wander around inconspicuously, if not surreptitiously, taking pictures - so it was a bit of a shock when the proprietor greeted me as soon as I parked and insisted on giving me a tour of the facility in his pickup truck. He's quite an intriguing character, and was very nice so I don't want to name him or his company...so we'll call him Cecil. He claimed to be the third-largest landowner in the area of the Marcellus shale as well as owning ranches in the hundreds of thousands of acres in the heart of the Bakken Formation of Montana, which are leased to mining and drilling interests (and where he has found piles and piles of fossils and arrowheads). In light of this I was curious why he had begun a landscape business and he told me the reason was so he could hunt as many deer as he wanted without state-imposed quotas or permits! Needless to say, he certainly does NOT think that pollution has anything to do with vegetation being in any sort of trouble.

The yellowing boxwood and arborvitae are, he claims, simply exhibiting their "winter color" - and the native ash trees that he does admit are languishing in the hedgerows dividing the plantation of trees are being killed by Asian Emerald Ash Borer. "But," I protested, "the invasion started in the midwest and even though it's been moving this way - they haven't arrived in eastern Pennsylvania yet. Plus, the ash trees are dying in New Jersey, and we haven't got beetles yet either!"

"Oh yes, they're here all right," he insisted.

Pines are thin and over-producing cones, a sign of stress.

I've heard the same silliness from New Jersey foresters. Faced with the "inexplicable" but undeniable death of ash, they invent a bug that isn't even here yet, let alone killing trees already...and of course they also ignore all the other species of trees that aren't even susceptible to the emerald ash borer but are dying for no apparent reason too. Oh wait, that's from the drought we're not having. Anyway, when I got home the next day, I called the PA Department of Agriculture and one obliging fellow there emailed me their latest report. Here are three of their illustrations, which indicate how closely the state entomologists are following the spread of a threat to this commercially valuable source of timber:

It's not because they aren't looking! The purple spots indicate traps.
The yellow dots indicate traps that caught Emerald Ash Borers in 2011 - none in Eastern PA or NJ

After the revelation about his extensive holdings of frackable land, Cecil told me that his son has a huge farm in New York, which the state wanted to use for the construction of wind mills. To thwart this abomination, Cecil - who, obscurely, claimed to find inspiration from the renegade spirit of Abbie Hoffman (whose body was found in a converted turkey coop nearby after his suicide) - devised a couple of diabolically creative means to obstruct this outrageous and wholly unnecessary imposition.

First, he filed for several balloon take-off permits, which gives the holder rights to airspace 5,000 feet above and of course, need windless conditions for take-off and landings...and then for good measure he filed environmental objections about wind turbulence adversely affecting the evapotranspiration of vegetation, and by extension, rainfall. Perhaps environmentalists should take note and learn how to similarly use obscure regulations to their advantage.

Grudgingly Cecil conceded, that multinational corporations control the US government - but meanwhile, he's making a huge amount of money off energy leases, and fervently believes an unfettered free-market should decide everything. As far as he's concerned, the methane being released "naturally" from permafrost in Alaska is far more significant a greenhouse gas than anything escaping from fracking...and by the way, rising temperatures have nothing to do with methane release...and more people get cancer from cigarette butts left on the side of the road than from industrial pollution.

Interestingly, he described the little hornbeams in the foreground that still have last year's leaves as dead.

In fact, Cecil doesn't think that there should be any governmental regulation or "interference" with activities that *might* cause pollution because 1. there isn't really any serious problem from pollution and 2. if there is, the remedy is to sue. That's right. Ordinary citizens are supposed to come up with the same amount of money for lawyers that giant corporations can afford, and then wait a few years for a decision from a corrupt judiciary that will let them off with a trivial fine.

Indigenous cedars are turning brown.

Which brings me to the subject of fracking. Now, I am always wondering what, if anything, has occurred to cause trees to die so rapidly. Yes, they have been dying in certain places from acid rain for over fifty years, but I never saw such universal damage to leaves until 2009. New research published in Nature is not the first to allege unregulated and undetected leaks of gas, but it is the latest to quantify it at extreme levels. "Air sampling reveals high emissions from gas field" describes the leakage of methane from fracked wells...and methane of course, is a precursor to ozone.

"Led by researchers at the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado, Boulder, the study estimates that natural-gas producers in an area known as the Denver-Julesburg Basin are losing about 4% of their gas to the atmosphere — not including additional losses in the pipeline and distribution system. This is more than double the official inventory, but roughly in line with estimates made in 2011 that have been challenged by industry. And because methane is some 25 times more efficient than carbon dioxide at trapping heat in the atmosphere, releases of that magnitude could effectively offset the environmental edge that natural gas is said to enjoy over other fossil fuels." Look at the difference between industry estimates of leakage and actual measurements!

I won't embed the video from which this screen shot of leaking gases came, because it's quite poor quality, but instead I transcribed a little portion of the talk by chemist Wilma Subra, a MacArthur fellow and former official of the EPA (who has been shot at for her efforts to educate the public about pollution). At this public hearing she describes what is allowed in terms of storage tank and pressure relief vent emissions after obtaining a permit to drill.

"Emissions from the condensate tank are really, really severe...volatile organic compounds are known and suspected to cause cancer. 25 tons per year of all the volatile organics at your production site under this permit by rule. 25 tons per year - sulphur dioxide...25 tons of nitrogen oxide...250 tons of carbon monoxide."

"So, the nitrogen oxide that you see listed combines with the volatile organics in the presence of heat and sunlight. So here in Fort Worth, in Dish, in Dallas and Louisiana we have lots of heat and lots of sunlight and they combine to form ozone. Ozone levels go up, people start having respiratory problems." And, I might add, trees have problems, too.

On the way home, I happened to pass the last remaining lumber mill in this area, so I stopped to look around. There is an old home at the entrance to the drive, surrounded by several dying trees. The pine tree in front is in pathetic shape.

The deciduous shade trees around the house are maples. Someone has been cutting back dying branches, to encourage new growth in the crown.

It's only a temporary reprieve of course, as the bark is falling from the trunks, meaning they cannot be saved.

This friendly gentleman told me one of his duties is to check each log with a metal detector. Frequently, especially in trees along roads, there is some nail or wire lurking, waiting to wreck an expensive saw. The hook below is deep inside this log. It's impressive what trees can absorb and yet still continue to grow unperturbed!

Following are some pictures of amazingly huge logs, interspersed with the transcript of a radio interview with Dr. John Reilly, from back in 2008, about his research at MIT. I've posted about his research before, but seeing how he describes it himself is much more of a revelation than reading the dry academic treatise. The most important aspect to me of course is that the decrease in annual crop yield and quality from exposure to ozone that he describes cannot be explained by the long-term drought that is purportedly the reason for global forest decline - according to forestry experts.

Question: Ozone is not only bad for the lungs, but it’s also damaging to plants. Ground level ozone turns their leaves brown and spotty, and stunts their growth. It’s particularly noxious to crops. Ozone has already cut cereal production in the U.S. by about five percent, and at the current levels could slash world crop yields nearly 40 percent by the end of the century. Those figures come from John Reilly – he’s associate director of the MIT Joint Program on the Science and Policy of Global Change. He led a recent study on ozone and crops, and joins me now in the studio. Hello, Dr. Reilly.

REILLY: Hello.

Question: I gather looking at your study that you see ozone pollution as not only a city problem, but a rural problem, and a global one at that.

REILLY: Many years ago when some of the first clean air legislation was passed, I think people thought it was very much as just an urban problem. When measurements have extended, people have realized that the ozone actually lives in the atmosphere for a few months, and so over that time it spreads out across the landscape and in fact, over the course of three months you can have a lot of transport around the entire globe. And so that means that ozone can appear at high levels in different places. The actual ozone levels, then, get higher because the background level is higher.

Question: Now as I understand it, leaves actually breathe, plants actually breathe. They have these stomata, these openings on their leaves in which they take in air and they let it out. What does ozone do to that process?

REILLY: That’s where the ozone actually enters into the plant. So the plant is trying to use CO2, and that’s one of its basic ingredients that allows it to grow. It’s a little bit like us breathing in, and when we breathe in to get air, that’s when we get ozone damage in our lungs. So it’s kind of a similar process in plants.

Question: So where there’s a lot of ozone, it’s like us trying to run in heavy traffic?

REILLY: Right. In fact, damage to crops tends to be larger than damage to, you know, other vegetation because we’re usually fertilizing crops, and fertilizing crops is getting them to grow really fast, and it’s like us going out and working really hard, or running really hard. So if you do that and then you have high ozone levels at the time, the damage to crops can be larger than unfertilized vegetation.

[note: when you consider the rampaging "nitrogen cascade", we are, in effect, fertilizing all vegetation!]

Question: So your study looked at not only ozone as an environmental factor, but also warmer temperatures, and the fact that there’s more CO2. Um, so what does this trio, associated with the use of fossil fuels, mean for agriculture?

REILLY: Well, the increase in CO2 is generally beneficial for plants. But changes in climate are, you know, sometimes good and sometimes bad. You know warming in northern areas tends to kind of increase the growing season and actually increase productivity. A lot of warming in the tropics can actually damage productivity. But ozone is damaging.

So we found that as a result of increasing ozone levels, the combination of these could be as much as a 50 to 60 or 70 percent yield decline in temperate regions in China, the U.S., and Europe. So that was a large net effect on crops, so the ozone effect was dominating there.

Question: How surprised were you by the results of your study?

REILLY: Well I was, you know, dramatically surprised that the results were so negative, and we checked them several times. There is a threshold, 40 parts per billion of ozone in the atmosphere, above which damage starts occurring. What really happened here is that the actual ozone levels only increased 50 percent, but when measured above this threshold, the amount of ozone increased by six-fold. So that was a dramatic increase and led to this high damage.

Question: So we’re in a time now when we’re seeing rising prices for food already, I guess in part due to the American dollar not being worth as much as it is and the price of oil going up. And now ozone is another factor to limit crop production?

REILLY: Yeah, and so I think, I mean ozone, and then our study actually found that climate change was largely beneficial but we’re not sure of that, because the climate predictions are so uncertain. So high variability in climate could be another negative effect on crops. And then one of the answers to some of these problems are biofuels. And if you had a substantial biofuels program, that would still put more pressure on land resources and food prices.

Question: What’s to be done?

REILLY: Well, it is possible to select plants that are less sensitive to ozone. But I think one of the key results of this study is this global or hemispheric transport of ozone. So while now individual countries can set standards for their own areas and hope to achieve them, in the future if we don’t control emissions elsewhere, then we will find it difficult to achieve those in our own backyard.

If there is a silver lining to the cloud, it’s that China is also going to experience crop damage from ozone, and it will be very much in their interest to reduce these pollution levels as well.

Note, Reilly says: "...it is possible to select plants that are less sensitive to ozone."

Can I make a couple of observations?

ONE: selecting crop cultivars genetically more resistant to ozone does nothing to save wild plants; and

TWO: It's bullshit anyway. Analogy: if you throw a bunch of people in the ocean they won't all drown at the same time. Translation: some are more or less sensitive than others.

But, given enough time and enough water, EVERYBODY will drown eventually. And so it is with plants in the inexorably rising levels of ozone. They're all going to drown, pretty much, in the toxic soup they are absorbing just as surely as drowning people inhale water. Just maybe not at the same exact moment.

It's outrageous that people like Cecil, as endearingly pugnacious as he is, can continue to deny that humans are capable of altering the atmosphere so much that it is changing the climate, and causing the ecosystem to collapse - ignoring the fact that evidence goes far, far back. In fact as this article written in 1885 from the archives of the New York Times indicates, it's just human nature to deliberately plot to make major changes in natural processes without ever bothering to pause and wonder about unintended consequences. This particular episode is quite funny, actually! The pictures are from the rest of my trip home.

"QUESTIONS OF CLIMATE."

"A well known engineer of this city has devised a plan for mitgating the severity of Winter and Spring in the North Atlantic States and warming the blue noses of our friends in Nova Scotia. The great warm current called the Gulf Stream surges by us on its northeasterly course, but it is commonly believed that the British Isles and Southwestern Europe get the benefit of it. With this stream almost within our reach we shiver and freeze through the Winter months and that horrible season called Spring, because a river of ice water from the glaciers of the pole pushes it away from our coast. Mr GOODRIDGE, the philanthropic engineer to whom we refer, proposes to dam this polar river in the Strait of Bell Isle and turn its waters eastward into the wide Atlantic. This strait, which separates Newfoundland from Labrador, is at one point only ten miles wide and one hundred and fifty feet deep. There he would invest $40,000,000 in a dam.

"He suggests that the interposition of this obstacle would raise the temperature of the coast from Newfoundland to Cape Hatteras. Invalids could pass their Winters at Cape Cod or on Block Island, the St. Lawrence Gulf and River would become navigable throughout the year, and the Newports of the future would lie on the shores of Nova Scotia. Giving free rein to his imagination, he sees the deflected polar current striking the Gulf Stream off the Banks of Newfoundland, bending it southward and compelling it to waste its warmth upon the shores of Africa."

"That there is a Gulf Stream has been demonstrated to the satisfaction of all reasonable men. Moreover, we know that there is a polar current pouring down from the north along the coast of Labrador and following the shore line as far south as Sandy Hook. But while this current hugs the coast not all of its waters pass through the narrow strait which Mr. GOODRIDGE proposes to dam. On the contrary, there is reason to believe that these waters for the most part pass outwards around the eastern shore of Newfoundland. The dam would be a source of great comfort to the people who inhabit the shores of the St. Lawrence Gulf, but New-England and New-York would still be in the cold. Mr GOODRIDGE'S plan is not complete. The dam would be a good thing in its way, but there should be added a jetty. This jetty should be extended eastward about 300 miles from Cape Race. This is the work to be done, and Capt. EADS is the man to do it."

"But Capt. EADS, who will grasp the idea as soon as it shall be presented to him in the proper way, will appeal to Congress for a guarantee of at least 3 per cent. per annum on the capital stock. Thereupon will arise a conflict between the bill for a transatlantic jetty and Senator BLAIR'S famous bill for changing the climate of North America. Possibly Mr. GOODRIDGE has heard of that bill. If not, he should send to Washington for a copy of Senate Bill 727, Forty-sixth Congress, First Session. Senator BLAIR proposes to extend the Gulf Stream northward through the Bay of Fundy, the St. Lawrence Gulf, and Labrador into Hudson's Bay, and to drive the warm waters of the Gulf of Mexico northward into the same bay by way of the channel of the Mississippi River."

The Frenchtown Bridge with New Jersey on the far side. That sign is for first daughter.
She liked to drive her carriage across on the way to watch polo games, stopping traffic on either side and infuriating motorists.

"Mr. GOODRIDGE'S plan, even when completed by the addition of the transatlantic jetty, is less complicated and would not be so costly as Sentaor BLAIR'S, but the Senator's would do a power of good and bring a large area of unoccupied land into market. Each of the plans has merits peculiarly its own. Still it would be unwise for our people to expend their energies upon both at the same time and therefore we suggest that the Senator and Mr. GOODRIDGE try to agree upon some scheme that will be mutually satisfactory."

The Delaware River

There is no indication of whether the British Isles or western Europe might have objected to the prospects of all that warmth being diverted and "wasted" on Africa instead of brought to temper their shores - and in any case, the plotters had only to wait for the warming that is now proceeding from greenhouse gas emissions.

I can never resist an architectural trainwreck, and so I was delighted to come across this phantasmagoric collection of a ravaged barn with it's crumpled, listing, battered sheds, some almost disappeared under shrouds of vines. The drive is now impassable from fallen branches impeding the way so I left my car at the road and picked my way through the tangle. The Norway spruce that line the entrance is thinning - the very first, on the left, has no needles at all.

The decay is illustrative in a number of ways. Whatever crisis led to the abandonment of this property happened fast, if the disarray is any indication, and hay still spilling from the loft...while at the same time the incremental festering collapse of the many outbuildings proceeded gradually and imperceptibly until suddenly, one day they were simply crushed beyond any hope of rehabilitation. Kind of like trees.

The most compelling impression, though, is that clearly once upon a time, somebody - most likely a family - built this beautiful barn with pride and love, and probably every expectation that it would always be tended.

Following is another article from the NYTimes archives, this one dating from 1970.

"Two weather scientists told their colleagues today that man was changing his environment without proper planning and ran a 'high risk' of destroying the basic relationships between living organisms and their surroundings."

"Frederick Sargent 2d, of the University of Wisconsin's College of Environmental Science, warned his fellow weathermen at a joint symposium here that the current method of 'ecological adaptation is not an appropriate strategy for managing the quality of the environment.'"

"Instead, he called for environmental planning and control motivated by 'the new humanism' that recognizes all men as common sharers of the environment and rises 'above provincialism in formulating a strategy for environmental control.'"

"His concern was later underlined by an afternoon speaker, Walter Orr Roberts, who listed a number of specific ways in which man and his technology seemed to be inadvertently changing the weather and environment."

Long ago, someone planted snowdrops and they have endured and spread.

"Mr. Roberts, president of the University Corporation for Atmospheric Research, in Boulder, Colo., said these changes were being caused by the following;"

"Megalopolises, with their effect on atmospheric and surface radiation."

"Heat dumping by air conditioners as industries and houses pump heat outdoors."

"A worldwide buildup of carbon dioxide caused by increased use of oil and coal fuels."

"Increased storm activity as a result of industrial smoke particles in the air."

"Sun reflecting cloud layers created by jet airliners."

"Both men were speaking on a the lat day of the three-day symposium, 'A Century of Weather Progress,' which was held to hoor the 10th anniversary of the United States weather services and the 50th anniversary of the American Meteorological Society."

"Mr. Sargent spoke about the current popularity of statements about the environment and said that none of these statements had yet answered the basic question: 'Shall the strategy be environmental control or ecological adaptation?'"

"He said that current indications implied that man was following a course of adaptation that had worked well as the environment had slowly changed and evolved over the centuries."

"This course, according to Mr. Sargent, involves, 'significant risks' because 'we do not know how individual species will adapt' and 'we do not know whether the ecosystem itself possesses the adaptability to accomodate to the changes that are being wrought by man.'"

"Environmental control and planning was suggested as an alternative and superior strategy by Mr. Sargent. He called for a 'consortia' of Government, industry, university and the public to develop that strategy successfully.'"

When I was peering through a window into the recesses of the barn to take that picture, I suddenly was enveloped in the most delicious, enticing scent of mint, and realized I was standing on a clump just beginning to emerge. Sure enough, it is starting to grow all around that corner of barn. I've never seen this variety before, with distinctively wide-bottomed arrow-shaped leaves...it smelled particularly sweet. I may have to go back with a trowel and dig some up for the garden at Wit's End.

But for now, on to Jockey Hollow. This day was only intermittently sunny. I should have known exactly how bad the condition of the woods at this former encampment would be, as soon as I approached the entrance. What was to follow was presaged by this sight. I walked about a two mile loop through the forest, and by the time I left, I was in tears.

Washington's Continental Army overwintered on this high ridge, which at the time was a farm belonging to Henry Wick producing hay, alfalfa, corn and fruit from an orchard. For three years during the Revolutionary War, from 1779 to 1782, the soldiers endured winters far worse than the infamous season at Valley Forge. Upon arrival the soldiers - those that didn't desert, die or mutiny - cut down over six hundred acres of trees in order to construct 1200 cabins, rudimentary furniture, and to burn. Now, the woods are comprised of mixed hardwoods including maples, oaks, beech, cherry, sycamore, and black walnut, among others. Some of them are huge. All of them are in various stages of decay.

Obviously some of these branches broke in the October snowstorm. But the vast, vast
majority of downed branches and trees fell well before then, and the fungus, holes, lost bark,
rotted centers and cankers also predate that storm.

" The deep snow was the keystone in the arch of starvation. We were absolutely, literally starved. For four days and as many nights I did not put a single morsel into my mouth except a little black birch bark I gnawed off a limb. Some boiled and ate their shoes. Some officers killed a pet dog for food. If this was not starving, I wonder what was."

Joseph P. Martin

Googling for more information about the prescient Walter Orr Roberts quoted in the article above led to a page from the American Institute of Physics. A well-known history written by Spenser Weart, it catalogs the discovery of global warming, and the role of aerosols. I'm going to reproduce the whole thing (without citations and quotations), because I had never read it before even though I'd heard of it (and plus, I took SO MANY pictures of trees dying at Jockey Hollow, I need to put something in between them!).

It's a fascinating chronicle of the struggles of scientists since the middle of the 20th century to account for the complexity of chemical reactions in the atmosphere and their effects on climate, which were by no means obvious in the beginning. What Weart calls "persistant ignorance" remains the state of current understanding of the production of ozone and its impacts on the ecosystem, unfortunately. And as far as I can tell, following decades of uncertainty about the relative effects on climate of CO2 and other emissions, and once it was recognized that warming from CO2 dominates aerosol cooling, CO2 became close to a single-minded focus for the scientific community. So although this is supposed to be about the discovery of CO2 causing global warming, it is just as much an explanation of how the other emissions and what they are doing to the biosphere have been forgotten.

For all the climate whizzes who read this primer ages ago, you can just skim through the pictures to the talk by Paul Gilding. But for chemtrail believers, it should be enlightening because the phenomena of lingering clouds from air traffic aerosols has been known to science long before any New World Order conspiracy to geoengineer, or poison useless eaters, was alleged.

Aerosols: Volcanoes, Dust, Clouds and Climate

Haze from small particles surely affected climate, but how? Old speculations about the effects of smoke from volcanoes were brought to mind in the 1960s, when urban smog became a major research topic. Some tentative evidence suggested that aerosols emitted by human industry and agriculture could change the weather. A few scientists exclaimed that smoke and dust from human activities would cause a dangerous global cooling. Or would pollution warm the atmosphere? Theory and data were too feeble to answer the question, and few people even tried to address it. Among these few, the uncertainties fueled vigorous debates, in particular over how adding aerosols might change the planet's cloud cover. Starting in the late 1970s, powerful computers got to work on the stupefyingly complex calculations, helped by data from volcanic eruptions. By the 1990s it was clear that overall, human production of aerosols was cooling the atmosphere. Pollution was significantly delaying, and masking, the coming of greenhouse effect warming.

In 1783 a volcanic fissure in Iceland erupted with enormous force, pouring out cubic kilometers of lava. Layers of poisonous ash snowed down upon the island. The grass died; three-quarters of the livestock starved to death, followed by a quarter of the people. A peculiar haze shadowed western Europe for months. Benjamin Franklin, visiting France, noticed the unusual cold that summer and speculated that it might have been caused by the volcanic "fog" that visibly dimmed the sunlight.

The sound of woodchippers followed me with their annoying racket.
The fact that these trails are maintained, and dying trees removed,
only makes the abysmal forest that remains so much more overwhelmingly tragic.

Better evidence came from the titanic 1883 explosion of Krakatau (Krakatoa) in the East Indies, which sent up a veil of volcanic dust that reduced sunlight around the world for months. The planet had so few weather stations that scientists were unable to learn for sure whether the eruption affected the average global temperature. But from then on, scientific reviews of climate change commonly listed volcanoes as a natural force that might affect large regions, perhaps the entire planet.

Looking at temperatures after major volcanic eruptions between 1880 and 1910, a few scientists believed they could see a distinct temporary cooling. (The most impressive confirmation came late in the 20th century, when examination of older records showed that the1815 eruption of Tambora, scarcely noted at the time outside Indonesia, had affected the world’s climate much more than Krakatau. Crops were frozen as far away as New England.)

[As usual, the branches that had fallen were especially covered in lichen.]

Perhaps the smoky skies in an era of massive volcanic eruptions were responsible for the ice ages, or had even killed off the dinosaurs by cooling the Earth? This image of climate change became familiar in popular as well as scientific thinking. In the 1950s, experts noted that the Northern Hemisphere had been getting warmer over the last several decades, a time when volcanoes had been relatively quiet, whereas the preceding century had experienced a number of huge eruptions and had been severely colder.

The Forest of Exploding Trees

The climate scientist J. Murray Mitchell, Jr. took up the question, with the help of improved data on how minuscule particles (aerosols) moved through the upper atmosphere. Studies of fallout from nuclear bomb tests had shown that fine dust injected into the stratosphere would linger for a few years, but would not cross from one hemisphere to the other. With that in mind, Mitchell pored over global temperature statistics and put them alongside the record of volcanic eruptions. In 1961, he announced that large eruptions caused a significant part of the irregular variations in average annual temperature in a given hemisphere. On the other hand, average temperatures had fallen since 1940, a period in which the world had seen few major eruptions. Mitchell concluded that the recent cooling was an "enigma." He thought it might signal a new phase of a decades-long "rhythm," the sort of cycle that generations of climatologists had tried to winkle out of their data.

Maybe aerosol science itself could solve the enigma. If it was plausible that volcanic emissions could alter the climate, what about particles from other sources? Meteorologists recognized that dust and other tiny airborne particles could have important influences. Simple physics theory suggested that such aerosols should scatter radiation from the Sun back into space, cooling the Earth. Through the first half of the 20th century, measurements and theory were inadequate to say anything about that. Speculation gradually came to focus on something that people were beginning to recognize as a major source of atmospheric particles: human activity.

Aerosols as Global Pollution (1920s-1960s)

Hints that human emissions made a difference in the atmosphere went back to measurements by the pioneering oceanographic vessel Carnegie and other ships on voyages between 1913 and 1929. Analysis of the sea air showed a long-term decrease in its conductivity, a decrease which seemed to be caused by smoke and gases from ships and perhaps from industry on land. "Thus we see," a researcher concluded, "that like a living thing, the conductivity of the lower atmosphere finds survival increasingly difficult in our modern industrial age." Still, a 1953 review concluded that scientists simply did not know whether pollution had significantly affected the transmission of solar radiation.

There was little prospect of getting an answer. Nobody had foreseen the need for a series of uniform measurements over the decades to show what was happening on a global scale. There existed only a few indirect indications, like the Carnegie's measurements of air far out at sea. It happened that some astronomical observatories had kept regular records of the clarity of the air at their sites. But nobody took on the challenge of hunting down such data and trying to correct the numbers for local changes such as the growth of a nearby city. As late as 1977, one expert lamented that "the time and energy put into discussion perhaps outweigh the time and energy which have been put into measurements." Worse, since air pollution seemed to be a problem only near the cities and factories where it was emitted, nobody had studied the relationship between pollution on the one hand and the chemistry of the global atmosphere on the other. The two fields engaged two different groups of investigators.

Aerosols not only intercepted sunlight, but might also affect climate by helping to create clouds. Research early in the century had shown that clouds can only form where there are enough "cloud condensation nuclei" (CCNs), tiny particles that give a surface for the water droplets to condense around. In the 1950s, scientists began to consider whether people might be able to deliberately change their local weather by injecting materials into the atmosphere to help clouds form. "Seeding" clouds with silver iodide smoke, in hopes of making rain, became a widespread commercial enterprise. Less visible to the public were government studies of the use of aerosols as a weapon of climatological warfare, to inflict droughts or blizzards on an enemy. For good or ill, it was becoming plausible that aerosols emitted on an industrial scale could alter the climate of an entire region.

Perhaps we were already doing something like that inadvertently. In the early 1960s, Walter Orr Roberts, a prominent astrophysicist at the University of Colorado, noticed that something was changing in the broad and sparkling skies above Boulder. Roberts had a long-standing interest in climate. One of the things that had driven his career in astrophysics was a hope of connecting climate with sunspot cycles; he had been especially impressed by the terrible drought of the 1930s, which he had seen firsthand when he drove through the Dust Bowl on his way to Colorado. Aerosols stayed on his mind.

One morning as he was talking with a reporter from the New York Times Roberts pointed out the jet airplane contrails overhead. He predicted that by mid afternoon they would spread and thin, until you couldn't tell the contrails from cirrus clouds. They did, and you couldn't. The Times made it a front-page story (Sept. 23, 1963). "Until recently, Dr. Roberts explained, cirrus clouds were thought to be more of an effect than a cause of weather conditions. But data from balloon and satellite experiments now suggest... [clouds] may trap enough heat beneath them to affect the weather." Since jets evidently made cirrus clouds, they "might be altering the climate subtly along major air routes."

The idea was controversial, like anything that sounded like "cloud seeding." Many scientists believed that seeding with particles could cause rain only under unusual conditions — or never. The "cloud chamber" studies around the start of the 20th century, which had shown that clouds could not condense in very pure air, did not seem significant. Most scientists believed that there were always plenty of nuclei in the air, from sources like soil dust stirred up by the wind and salt crystals from ocean foam. Therefore clouds would form wherever the temperature and humidity were right. Nobody had carefully tested this assumption. The theory of how particles affected clouds was complex beyond reckoning, and field tests were too costly to pursue far, especially since their results turned out to be contradictory and confusing. Scientists avoided the intractable study of cloud formation. As one of them later recalled, they viewed tiny particles mainly "as air-quality indicators.

By the early 1960s, however, the question of human influence on clouds was starting to attract at least some scientific attention. Roberts's observation of contrails was joined by other hints that various types of anthropogenic aerosols — microscopic solid particles or droplets of chemicals produced by human activity — might indeed increase the amount of cloud cover. A 1966 study of satellite photos of the oceans found linear clouds that might have been seeded by smoke from ships. Another study, tracking rainfall downwind from paper mills, suggested that humans were causing more precipitation inadvertently than by deliberate cloud seeding. These were not global but local or regional effects, and speculative at best.

Another line of thinking about the effects of dust from human activities addressed pollution that settled on ice and snow. Could that lower their reflectivity enough to change the climate? The idea was inspired by one of those quirky speculations that both harassed and stimulated climate scientists — a suggestion that "dusting of the ice caps" by volcanoes and soil blown off of dry lands had caused the irregular changes in sea-level that had been recorded in historic times. This was only one of countless theories of climate change, and did not get much credence or attention.

Roberts's tentative ideas about clouds did get a chance to catch sustained attention. The opportunity was a growing public concern over the U.S. government's plans to build a fleet of supersonic transport airplanes. Hundreds of flights a year would inject water vapor and other exhaust into the high, thin stratosphere, where natural aerosols were rare and any new chemical might linger for years. Some scientists feared that the flights would seriously affect the climate. A 1970 review by a panel of experts warned that aircraft were already polluting the stratosphere with hydrocarbons and sulfur and nitrogen compounds, all of which might interfere with radiation directly as well as increasing cloudiness. They reported that high cirrus clouds had in fact increased in the United States since the 1940s. The effects of aircraft on climate might be significant, they concluded — indeed particles emitted by a fleet of supersonic transports might alter the stratosphere as much as a volcanic eruption. But a calculation of the actual effects was still far beyond reach. Such work was admittedly closer to plausible story-telling than scientific rigor.

Aerosol science was just emerging as a field standing on its own. Like many other fields it had gotten a strong impetus from warfare, where smokes, poison gases, and disease-carrying aerosols could be mortal concerns. The field first began to coalesce during the Second World War, and its first handbook was based on studies done under the Manhattan Project. After the war rainmaking jumped to the top of the list of practical interests, but it was too intractable and controversial for most aerosol specialists. Still less were they interested in tackling the physics of clouds or the physics of radiation high in the atmosphere — topics that were dauntingly intractable and remote from any useful application. Concern over fallout from nuclear weapons tests motivated some research (not always openly published) that was potentially relevant to climate. Most aerosol specialists, however, were far more interested in the practical problems of air at ground level, especially public and occupational health. And these problems, involving dust and pollution, "had no glamour to offer for young researchers," as one pioneer admitted. The field's first journal (named, naturally enough, the Journal of Aerosol Science) was not founded until 1970, and the editor remarked that even then "academic status has not been achieved."

The people who were coming together to form an aerosol science community were mostly scattered among industrial and government laboratories. In these organizations, as the new journal's editor remarked, "it is extremely difficult for a scientist to concentrate over the many years which are necessary for the mastery of a subject." Many of the aerosol experts were kept busy studying local air pollution, driven by rising public dismay over urban smogs. Chemists were drawn in during the 1950s to analyze the smog of Los Angeles, which turned out to be a fascinating (and sometimes lethal) mixture of chemicals as well as solid particles. Meanwhile other aerosol experts worked on industrial processes like "clean rooms" for manufacturing electronics, and still others investigated military problems such as the way particles scattered laser light. These researchers had only occasional contact with their colleagues in different areas of the proto-field of aerosol science, and still less with anyone in other fields of science that might relate to climate.

Most of the aerosol scientists' attention went to "pollution" particles that fell out of the atmosphere (or were washed out by rain) within a few days. But other microscopic particles could linger longer and travel farther. Entire regions were intermittently hazed over, raising questions about possible world-wide effects. Already in 1958, one expert had remarked that "there can no longer be any sharp division between polluted and unpolluted atmospheres." It was some time before many others recognized how far pollution spread beyond cities. Understanding came only after people studying smog set up a network of stations that regularly monitored the atmosphere's turbidity (haziness). In 1967, Robert McCormick and John Ludwig of the National Center for Air Pollution Control in Cincinnati reported a gradual increase in the general turbidity over regions spanning a thousand kilometers. Further checks of the record of turbidity turned up hints of increases even in remote areas like Hawaii and the North and South Poles. Could humanity's emissions be affecting the global climate, not in some abstract future but right now?

Although these studies were not widely noted at the time, they contributed to, and at the same time responded to, a broad change of public thinking. This had started with observations that radioactive fallout and chemical pesticides could be found far from the places where they were emitted. The world's oceans and air could no longer be seen as a virtually infinite dumping-ground. Fewer and fewer people believed that the atmosphere could safely absorb (as one aerosol expert acidly put it) "any effluents which mankind might see fit to disgorge into it." Through the early 1960s, ideas about human influence on the global climate had focused on greenhouse effect warming caused by industrial emissions of carbon dioxide gas (CO2). At the time the effect seemed no more than a fuzzy speculation. Adding to the uncertainty, weather experts were just now confirming that a world-wide cooling trend had been underway for a decade or so. McCormick McCormick and Ludwig suggested that the cooling trend itself might be due to human activities.

[Approaching the historic homestead - notice, every single tree on the way has evidence of terminal decline.]

[Cankers, holes and rotted bark - all are present, not a tree is spared.]

Reid Bryson, a University of Wisconsin meteorologist, joined the discussion. In 1962 , while flying across India en route to a conference, he had been struck by the fact that he could not see the ground — his view blocked not by clouds but by dust. Later he saw similar hazes in Brazil and Africa. The murk was so pervasive that local meteorologists took it for granted and failed to study it. Bryson realized, however, that the haze was not some timeless natural feature of the tropics. He was seeing smoke from fields set on fire by the growing population of slash-and-burn farmers, and dust from over-grazed lands turning to desert. The effects of ever more widespread farming and grazing, together with pollution from industry, seemed large enough to alter the climate of a region or even the entire planet. At a 1968 "Symposium on Global Effects of Environmental Pollution" that met in Dallas, Texas, Bryson impressed his colleagues with a chart that showed how rising levels of dust in the Caucasus correlated with the rising output of the Russian economy. He went on to speculate that a rapid and world-wide rise of atmospheric turbidity would cause temperatures to fall. Calling for more intense study, Bryson and a collaborator wrote that they "would be pleased to be proved wrong. It is too important a problem to entrust to a half-dozen part-time investigators."

Plenty of firewood now!

Concern grew when studies showed that recent decades had seen a great increase in the amount of aerosols in the lower atmosphere ("troposphere"). The air over the North Atlantic was twice as dirty in the late 1960s as it had been in the 1910s, suggesting that the natural processes that washed aerosols out of the atmosphere could not keep up with human emissions. As a back-page New York Times item (Oct. 18, 1970) reported, "This is disturbing news for those weather experts who fear that air pollution, if it continues unchecked, will seriously affect the climate..."

The orchard. The cages are around young replacements for the deceased.

But how much of the haze was really caused by humans? In 1969 Murray Mitchell pushed ahead with his statistical studies of temperatures and volcanoes. He calculated that about two-thirds of the cooling that had been progressing in the Northern Hemisphere since 1940 was due to a few recent volcanic eruptions. He concluded that "man has been playing a very poor second fiddle to nature as a dust factory." Other respected climatologists agreed that volcanic dust could account for a substantial part of the temperature variations in the last century or so. The most impressive work was done by the British meteorologist Hubert Lamb, who burrowed through many kinds of historical records to compile a "Dust Veil Index." His tables revealed a telling connection between dust and cooler temperatures. But if the experts now agreed that volcanic explosions could affect temperature, they disagreed on how strong the effect was.

One thing scientists were coming to agree on was that the problem was significant enough to merit a sustained attack. Mitchell for one, even while denying that human aerosols had done much so far, thought they could become significant within a few decades. McCormick and Ludwig told a New York Times reporter (June 9, 1970) that their experiments proved that fine particles could noticeably reduce the sunlight reaching the surface of the Earth. Their main message was a call for better monitoring of turbidity. "What we are trying to do," Ludwig added, "is get scientists' curiosity and concern aroused."

Warming or Cooling? (Early 1970s)

A few scientists did have their curiosity and concern aroused to the point where they pursued a modest number of studies in the early 1970s. They failed to find solid evidence for a global increase of turbidity. But the studies did confirm that there were regional hazes — episodes of pollution spreading a thousand kilometers or so downwind from industrial centers. Everyone now admitted that human pollution was growing headlong. While Mitchell continued to insist that humanity was "an innocent bystander" in the cooling of the past quarter-century, in 1971 he calculated that our emissions might begin to cause substantial cooling after the end of the century. Other scientists claimed that the increase of aerosols was important already, perhaps even more of a concern than CO2. But nobody trusted anyone else's calculations, which were in fact much too crude to give reliable answers. Adding to the uncertainty, Mitchell gave plausible arguments that aerosols could produce a warming effect. It depended on how much they absorbed or reflected radiation coming down from the Sun, and how much they trapped heat radiation rising up from the Earth's surface. It also depended on the height in the atmosphere where the aerosols floated, and on whether they floated above bright regions like deserts (which reflect sunlight) or dark ones like the oceans (which absorb sunlight).

[A closeup of the trunk - it's pretty obvious why so many have been removed and replaced.]

S. Ichtiaque Rasool and Stephen Schneider entered the discussion with a pioneering numerical computation. (This was the first atmospheric science paper by Schneider, who would become a well-known commentator on global warming. As an engineering graduate student, he had been alerted to environmental issues when he heard a talk by the biologist Barry Commoner, warning that pollution could trigger either an ice age or global warming.) Rasool and Schneider, like Mitchell, recognized that aerosols might not cool the atmosphere but warm it; the tricky part was to understand how aerosols absorbed radiation. Their calculation gave cooling as the most likely result. Estimating that dust in the global atmosphere might have doubled already during the century, and might double again in the next fifty years, they figured that this might cool the planet by as much as 3.5C.

That could be disastrous, especially in view of some simplified calculations just published by others which suggested that the climate system could be very sensitive to small changes of temperature. Rasool and Schneider also believed the greenhouse effect would not counteract the cooling, since according to their model, adding even a large amount of CO2 would bring little warming. The dip caused by aerosols, they exclaimed, "could be sufficient to trigger an ice age!" In fact their equations and data were rudimentary, and scientists soon noticed crippling flaws (as did Schneider himself, see below). But if the paper was wrong, what did aerosols in fact do?

Another stimulus to work on aerosols came from a spacecraft that reached Mars in 1971 and found the planet enveloped by a great dust storm. The dust had caused the Martian atmosphere to warm up substantially — an undeniable demonstration that aerosols could profoundly affect climate. New studies confirmed how aerosols could affect a planet's reflectivity, by scattering and absorbing sunlight and by catching infrared rays coming up from the surface. Yet the calculations were still too uncertain to say for sure whether the net result would be to increase or decrease the reflectivity, whether dust would cool the Earth or warm it.

Beyond the direct effects of aerosols absorbing or scattering radiation, an even tougher puzzle remained: how did particles help create particular types of clouds? And beyond that loomed the enigmatic question of how a given type of cloud might affect the temperature. Depending on whether clouds were thick or thin, and where they floated in the atmosphere, they might bring some amount of cooling, by reflecting sunlight, or they might even bring warming, by trapping heat radiation in a sort of greenhouse effect. The one sure thing was that aerosols could make a difference to climate, and perhaps a big difference.

Bryson felt more certain than most about the effects of aerosols, and more worried. His studies of the distant past had convinced him that the climate had sometimes veered dramatically in the span of a single century. Could a similar cataclysm befall our civilization? Weren't the deadly 1973 droughts in Africa and South Asia a sign that we were destroying our climate with pollution? In 1974, Bryson noted that humans emitted aerosols mostly in northern mid-latitudes, just where the recent cooling trend was most evident. He suggested that the pattern of pollution would change the gradient of temperature from equator to pole. A change of only a few tenths of a degree in this gradient, he calculated, could shift the entire general pattern of atmospheric circulation. That might alter, for example, the annual monsoon that was crucial for the peoples of India and the African Sahel. "Our climatic pattern is fragile rather than robust," he warned. Bryson was taking his concerns to the public. The entire balance of climate could be tipped, he said, by aerosols pouring from what he called "the human volcano." (He meant our emissions of aerosol particles and chemicals, not CO2. The amount of the gas coming from volcanoes was negligible, barely as much in a century as what human industry emitted each year.)

[This one split because it was rotted inside.]

To the confusion of onlookers, an entirely different prediction about cooling was meanwhile emerging from an entirely different field of science. New data on past ice ages showed that they followed a remarkably regular schedule. The warmest part of a cycle typically lasted barely ten thousand years, so it seemed likely that the Earth was now past the peak of the current cycle and was scheduled to descend into another glacial epoch. (Decades later it was learned that the current cycle is atypical, likely to last a few tens of thousands of years, but nobody at the time could guess that.) In the natural course of things the temperature would fall gradually over the next few thousand years. But perhaps human emissions were getting large enough to interfere with the natural process. Would greenhouse gases prevent the projected cooling? Or would pollution accelerate it?

Newspapers and television in the early 1970s were regularly running stories on the appalling droughts in the Sahel and elsewhere, and the public was starting to worry about climate change. Would more dust and gases of human origin afflict us with even more deadly droughts or floods? That depended critically on the effects of aerosols. The scientists who had studied this recondite topic began to feel the public eye upon them, and they debated their technical questions with heightened intensity. They increasingly saw that it was theoretically possible for a small change of conditions to bring large changes of climate. But it would be another three decades before computer models of climate became good enough to confirm that human pollution probably had in fact contributed to the Sahel drought. Few experts were more than halfway convinced by Bryson’s argument that the "human volcano" was liable to cause a disastrous global cooling.

The prominent meteorologist William W. Kellogg, for one, told a 1975 World Meteorological Organization symposium not to worry. He noted that industrial aerosols, and also the soot from burning debris where forests were cleared, absorbed sunlight strongly — after all, smog and smoke are visibly dark. They would thus retain heat. He calculated that the chief effect of human aerosols would be regional warming (although he admitted that the calculation relied on properties that were poorly known). Anyway, as Kellogg also pointed out, rains washed aerosols out of the lower atmosphere in a matter of weeks. Eventually the warming due to the increase in CO2— a gas that lingered in the atmosphere for centuries — must necessarily dominate the climate.

Similarly, Stephen Schneider and a collaborator improved his rudimentary model, correcting his earlier overestimate of cooling by checking against the effects of dust from volcanoes. They got a decent match to temperatures over the past thousand years, after they added an estimate for changes of solar intensity. The model now predicted that "CO2 warming dominates the surface temperature patterns soon after 1980." Only a few people pointed out that pollution might cancel out some of the greenhouse warming, delaying the time when it would become obvious.

Bryson and his co-workers continued to insist that smoke from burning fossil fuels and forest clearing had a powerful cooling effect. After all, the haze visibly dimmed the solar radiation that reaches the surface. They expected pollution would more than balance the effects of increased CO2, since the more fuel humanity burned, the more aerosols were emitted along with the gas. Taking everything into account, they calculated that "an expected slight decrease in surface temperature" was already underway. Bryson would not concede that his group's observations, analysis of data, and theoretical understanding were too uncertain to produce a definitive answer. The real value of this work was not in the purported findings, but in the way it forced scientists to pay attention to a topic that was indeed highly important.

Most of the studies were not even addressing all the key problems. Ideas about human emissions focused on an image of dark smog and smoke obscuring the sky. Some scientists pointed out, however, that such direct effects of particles interfering with radiation could be outweighed by indirect effects. They emphasized new observations that nuclei for the condensation of water droplets into rain or snow were sparse under natural conditions.

Thus "the most sensitive" leverage point for pollution particles might be their role as cloud condensation nuclei. "Although the changes are small," one scientist remarked, "the long-term effect on climate can be profound." Conceivably the clouds would reflect away so much sunlight that the whole climate system would flip into a new ice age. An important 1975 review panel concluded that the impact of particles on global temperatures "cannot be reliably determined," for it depended on many factors that were scarcely known. Warning that the particle load in the atmosphere might rise another 60% by the end of the century, they called (in the usual fashion of study groups) for further study.

So it continued, as some scientists concluded that aerosols would cause warming, others expected cooling, and still others expected no significant global effect. One widely noted example was a survey of dusty days in Arizona by Sherwood Idso and Anthony Brazel, who concluded that additional aerosols from human activity would warm the Earth. They urged people to abandon any thought that industrial pollution would serve as a brake on CO2 greenhouse warming. Critics promptly tried to poke holes in the study's limited data.

Epicormic branching - a flush of whorls from the main stem, indicative of a dying tree.

Another group analyzed global weather statistics, found that the recent drop in temperatures was restricted to northern latitudes, and argued that this demonstrated a cooling effect of industrial particle emissions, which were far greater in the Northern Hemisphere. This approach too was quickly criticized, for lack of enough data on Southern Hemisphere temperatures.

Many other studies invoked physical models, data, and the history of volcanic eruptions and the ice ages as they debated the relation of particle size to albedo (reflectivity), clouds, and temperature. Like most aspects of climate studies, only even more so, progress on aerosol impacts would require help from many different fields.

In 1977 some light was cast into the shadows by Sean Twomey at the University of Arizona's Institute of Atmospheric Physics. (The name of the institute hints how scientists were regrouping to attack complex questions involving the environment.) Twomey showed that reflection of sunlight from clouds depends on the number of nuclei in a curiously intricate way. Adding particles would normally create more water droplets, and thus thicker light-reflecting clouds. Past some point, however, the drops might fall as rain and the clouds would disappear altogether. On the other hand, if there were a great many nuclei the water could end up not as raindrops but as myriads of tiny droplets — a long-lasting mist. And as Twomey also showed, the amount of reflection and absorption depended strongly on the average size of the droplets (with smaller mist droplets there is more surface area for a given amount of water).

[A deer skeleton - one of three I saw.]

[I think it likely the deer are starving to death. Gone are the days when I saw great herds of them.]

[Here is the only live deer I saw. In the middle of the ^^ picture! Other than that I saw one chipmunk, two birds, and that's it for wildlife for the entire time.]

In short, adding more aerosol particles might either raise or lower cloud reflectivity, depending on quite a variety of factors. Overall, for thin clouds Twomey calculated that added pollution would increase the reflectivity (and thus cool the climate), whereas for thick clouds absorption would dominate (hence warming). He concluded that since thin clouds are most common, the net effect of human pollution should be to cool the Earth.

This did not close the debates. As another pioneer recalled, "Twomey's insights were largely ignored by the climate modeling community — perhaps because it seemed unlikely that such a simple analysis could capture the behavior of such a complex object as a cloud."

Besides, to figure out the effects on the world's climate, in principle you would need to start with a map of the globe showing for each region the amount of every type of smoke and dust particle and industrial pollutant in each layer of the atmosphere. Next you would have to calculate the direct interaction of each type of particle or chemical molecule with sunlight, and also calculate the effects of each type in forming various types of clouds, and finally calculate how each kind of cloud interacted with visible and infrared sunlight. Little was known about any of this.

The debates made one thing clear: climate change could not be properly understood without a better grasp of aerosol effects. When scientists made theoretical calculations of scattering, the results were often at odds with field and laboratory measurements. It was not clear whether the theories or the measurements were wrong — if not both. Much more work would have to be done to get even the most basic data, such as how the various kinds of particles of various sizes scattered or absorbed light of various wavelengths. Several groups undertook these measurements in the 1970s, using instruments that, like so much in aerosol science and the rest of geophysics, could be traced back to a military application.

All this was only the most simple, basic-physics aspect of aerosols. Studies increasingly confirmed that there were more complex ways that particles would surely affect the climate. A surprising example showed up in the 1974 international GATE experiment, in which scores of research ships and aircraft crisscrossed the tropical Atlantic. They found that when winds blew dust from the Sahara desert over the ocean, significant changes in weather and the radiation balance could be seen all the way to the American coast.

The best clues of all came from observing how volcanic eruptions acted on climate. Historical research covering the past two centuries was confirming a distinct, if weak, pattern of global cooling in the few years following each major eruption. Better still, dust from volcanoes and other sources was found in layers of ancient ice, drilled from the frozen plateaus of Greenland and Antarctica. The dust in the ice cores correlated with Lamb's volcanic "Dust Veil Index" and extended much farther back. Temperatures too could be read from the layers of ice, and analysis showed that through the past hundred millennia, dustier air had correlated with cooler polar regions.

To be sure, that might only mean that cooler periods were windier, bringing dust from afar. But it seemed likely that volcanoes did have a direct impact on climate. (Later, more comprehensive studies tended to confirm that. For example, a dearth of major eruptions over several centuries may have helped cause a "Medieval Warm Period" that affected large parts of the planet — notably the North Atlantic region, when the Vikings benefitted from a benign climate to establish a colony in Greenland — although changes in solar activity were probably at least as important.)

None of this supported the claims that we risked hurling ourselves into a new ice age—claims more common in excited news articles than in the scientific literature. Few scientific papers were published in the early 1970s on any topic related to climate change on a human time-scale, that is, faster than the thousands of years that most scientists thought glacial ages took to evolve. Only a small fraction of these few papers projected cooling within a century or two. During the second half of the 1970s the pace picked up as scientists published several dozen papers about century-scale global climate change. Some of these papers discussed cooling and warming factors without coming to a conclusion, but more than half projected that greenhouse warming would dominate. A study of the peer-reviewed articles of the period found that "global cooling was never more than a minor aspect of the scientific climate change literature of the era." (As described below, scientists in the 1990s with far better data and computer models concluded that industrial haze along with volcanoes had indeed helped to depress Northern Hemisphere temperatures for a few decades in the mid 20th century, while warming from the accumulated greenhouse gases began to dominate in the 1980s.)

By the late 1970s hardly any scientist was arguing that cooling was likely to become severe. The major industrial nations had put "clean air" laws in place. Given that particles were washed out of the lower atmosphere in weeks, pollution was not going to double and redouble as some had feared. Moreover, improved computer models of climate had convinced many that CO2 added to the atmosphere must bring a global warming. The effect would be increasing rapidly along with the relentless rise of CO2, which humanity was emitting far more rapidly than anything could remove it from the atmosphere.

Sulfates, Soot and Clouds (mid 1970s-1980s)

As scientists calculated the physics of aerosols more accurately, they realized they could not figure out any way that smoke and dust particles from a volcanic eruption could cause long-term effects on temperature; they should drift to the ground or be rained down in a few weeks. Then how did volcanoes affect climate for a year or even two? The answer was hidden in something else thrown into the air.

When thinking about aerosols, the public and most scientists had attended chiefly to the visible and obvious. That meant the fine carbon soot making up smoke from factories, slash-and-burn forest clearing, and natural forest fires; mineral dust from dried-out soil (perhaps increased by human agriculture); and other solids such as salt crystals from ocean foam. When scientists thought about climate change that volcanic eruptions might cause, they chiefly considered the minute glassy dust particles that snowed down thousands of miles downwind from an eruption.

Well into the 1970s, meteorologists concerned with aerosols mostly continued to assume they were dealing with such coarse mineral particles. However, anyone looking at city smog — or smelling it — might guess that chemicals could be a main component of a haze. The intense studies of urban smog that began in the 1950s focused the attention of a few scientists on the production and evolution of simple chemicals.

One of the most important of these molecules was sulfur dioxide, SO2. Emitted profusely by volcanoes as well as by industries burning fossil fuels, SO2 rises in the atmosphere and combines with water vapor to form minuscule droplets and crystals of sulfuric acid and other sulfates. The particles reflect some of the radiation coming from the Sun and absorb some of the heat radiation rising from the Earth's surface.

To the considerable surprise of atmospheric scientists, studies in the early 1960s suggested that sulfuric acid and other sulfate particles were the most significant stratospheric aerosols. This was something that could linger high in the air for years, like the fine fallout particles injected by nuclear weapon tests.

The sulfate haze was in fact especially thick for a few years following a huge volcanic eruption in 1963, when Mount Agung in Indonesia blasted some three million tons of sulfur into the stratosphere. That was an order of magnitude more sulfur than human industry produced in a year, and most specialists thought human emissions of sulfates must be comparatively unimportant. Flights in the stratosphere in the early 1970s (part of a huge government effort to study whether airplanes might harm the ozone layer) conclusively confirmed that the principal aerosol there was droplets of sulfuric acid, presumably from volcanoes.

Outside the smoggy cities, haze was commonly assumed to be a "natural background" from soil particles and the like, with occasional extra material from volcanoes. That was challenged in 1976 by two leading experts, Bert Bolin and Robert Charlson. Analyzing air purity data collected by government agencies, they showed that sulfate aerosols from industrial centers seriously affected wide regions downwind. Sulfates dimmed the sunlight not only in cities but across much of the eastern United States and western Europe. This confirmed what McCormick and Ludwig had reported a decade earlier, a widespread haze somehow connected with urban smog.

Bolin and Charlson drove their point home with some calculations. Although they repeatedly admitted that the data were fragmentary, and the theory so oversimplified that they could be off by a factor of ten, their results strongly indicated that sulfates were a significant factor in the atmosphere. Indeed among all the aerosols arising from human activity, sulfates played the biggest role for climate. The old view of aerosols as simply a dust of mineral particles had to be abandoned. In fact the haze was a mixture of the dust with tinier chemical droplets.

Still, the effect seemed minor. Bolin and Charlson figured that human sulfate emissions noticeably affected scarcely one percent of the Earth’s surface. The sulfates were cooling the Northern Hemisphere by scarcely one-tenth of a degree. Most scientists thought that was negligible (even if the calculations were accurate, which seemed unlikely).

It's not just the big old trees that are rotted inside - young trees are as well.

They continued to assume that the problem of human aerosols was strictly local, or at worst regional. Bolin and Charlson themselves, however, noted that sulfate emissions were climbing steeply. They warned that "we are already approaching the time when the magnitude of the indirect effects of increasing use of fossil fuel may be comparable to the natural changes of the climate over decades and centuries."

Sulfates were a new worry for the scientists who were concerned about future climates. That included in particular the Russian expert Mikhail Budyko. In 1974, he suggested that if global warming became a problem, we could cool down the planet by burning sulfur in the stratosphere, which would create a haze "much like that which arises from volcanic eruptions." He calculated that just a few airplane flights a day would suffice. That kind of freewheeling speculation was about all one could do at this point in thinking about sulfates.

The question attracted few workers, if only because the prospects were poor for solid, publishable studies. For one thing, the amount and type of aerosols (unlike CO2) varied greatly from region to region. For another, their net effect on the radiation balance depended on the angle of sunlight (the low-angle illumination of Arctic zones doesn't interact with clouds in the same way as the plunging rays of the tropics). And so forth. The only thing likely to get anywhere would be a full-scale computer attack.

In the mid 1970s, when some groups managed at last to develop computer models that plausibly connected climate to the level of greenhouse gases, a few groups tried to apply these models to study the effects of aerosols. First they needed reasonably accurate information on the spectrum of aerosols normally in the atmosphere — the sulfuric acid droplets, salt crystals, rock dust, soot, and so forth. What were the sizes of the particles, their chemical composition, and their effects on radiation at various heights in the atmosphere? There were far fewer observations than the scientists needed, but some approximate numbers were laboriously worked out in a form usable for modeling studies.

The scientists also had to give up their preoccupation with the smog-ridden lower atmosphere, considering also the clear stratosphere. A few extra particles there, lingering for months, could make a big difference to the passing radiation. Despite daunting theoretical complexities and ignorance of many aerosol properties, the enterprise made progress. Different groups of modelers, using different techniques, converged on some tentative ideas.

The first big idea was confirmation that the formation of clouds was not already saturated by natural aerosols. Thus adding some particles to the atmosphere should noticeably affect climate. The second big idea was that the net effect of adding aerosols, an effect which could now be reliably calculated, was to increase the planet’s reflectivity and thus bring modest cooling.

Especially impressive was work published in 1978 by a NASA group under James Hansen, studying how climate had changed after the 1963 Mount Agung eruption. They found that the changes calculated by their simple model corresponded in all essential respects — including timing and approximate magnitude — to the observed global temperature changes. Hansen undertook the study mainly to check that his climate modeling was on the right track. But the results also showed that "contrary to some recent opinions," volcanic aerosols could significantly cool the surface.

Another sign that sulfates mattered came literally from another planet — Venus. The hellish greenhouse effect that astronomers observed there could not be caused by CO2 alone, and during the 1970s, sulfuric acid was identified as a main force in the planet's atmosphere. Another telling sign came from a 1980 study of Greenland ice cores. The level of sulfuric acid in the layers of ice pointed directly to ancient volcanic eruptions. Where clusters of giant eruptions were found, there had been episodes of cooling ("which further complicates climatic predictions," the authors remarked).

The feeling that scientists were getting a handle on aerosols was strengthened in 1981 when Hansen's group fed their computer model a record of modern volcanic eruptions. They combined the temporary cooling effect of volcanoes with estimates of changes due to solar variations and, especially, to the rising level of CO2.

The net result fitted pretty well with the actual 20th-century temperature curve, adding credibility to their model's prediction of future global warming. (This result was robust: vastly more sophisticated computer models at the end of the 20th century continued to get a good match to modern temperature fluctuations if, and only if, they added together eruptions, solar activity, and the rise of greenhouse gases. Adding industrial aerosol pollution would further improve the match.)

The cooling effect of sulfates was confirmed by computer studies that took advantage of a colossal explosion of the Mexican volcano El Chichón in 1982. From this event scientists learned more about the effects of volcanic aerosols, one of them declared, "than from all previous eruptions combined." Satellite observations of clouds that were affected by the eight million tons of sulfur aerosols blown into the upper air could be matched with a noticeable cooling of regions beneath the clouds.

Alongside the progress in dealing with volcanoes came increasing evidence that the natural background of aerosols always present in the atmosphere also tended to cause mild cooling. The first calculation that many experts accepted as reasonably accurate gave a year-in, year-out global cooling effect of 2-3°C (roughly 4-5°F).

These calculations, however, dealt only with the effects of aerosols directly on radiation. They included cloud cover (if they calculated it at all) as a simple consequence of the moisture in the atmosphere. But since the 1960s, a few scientists had pointed out that the direct effects of aerosols might be less important than their indirect effects on clouds. This was the kind of thing Walter Orr Roberts had talked about, when he had pointed to cirrus clouds evolving from jet contrails. These clouds had seemed a temporary, local phenomenon. Now some wondered whether human emissions, by adding nuclei for water droplets, might be causing more cloudiness world-wide?

These speculations had been reinvigorated in 1979, when a pair of scientists at the University of Utah had managed to insert aerosols and cloudiness in a reasonable way into a basic radiation-balance computer model. The researchers confessed that their calculation was massively uncertain. But if the worst case was correct, then increased cirrus clouds could lower the Earth's surface temperature several degrees. It was another case of scientists warning that we might "initiate a return to ice age conditions."

Other scientists, in particular Hansen's group, doubted that aerosols could be so powerful. While admitting that nobody knew how to model cloud feedbacks reliably, they concluded that aerosols from human activity and even from volcanoes could not produce enough cooling to halt the "inevitable" warming by greenhouse gases.

Progress would depend upon more accurate knowledge of the intricate chemistry of the atmosphere. In the 1980s, aerosol physicists and atmospheric chemists finally established close contacts. It was becoming clear that the most important aerosols humanity produced were not dust and smoke particles, but products of chemical reactions of the gases we emitted, an almost unknown topic. As usual, recognition of an important area of ignorance drove rapid improvements in measuring instruments and also in theory (which by now was done mostly through computer models).

One important finding in the early 1980s was that human chemical emissions tended to turn into sulfate particles whose sizes fell exactly within the range most effective for scattering sunlight. Thanks to research on atmospheric quality sponsored by environmental protection agencies, scientists increasingly agreed that regional sulfate hazes were a serious issue. Since the mid 1970s, studies had proved that such hazes could significantly dim sunlight for thousands of kilometers downwind from the factories. But the effect on the rest of the planet's climate, if any, remained debatable.

The need to resolve the problem was driven home by undeniable evidence that dimming of sunlight by aerosols was increasing all across the Northern Hemisphere. (One estimate, which few believed, put the reduction as high as 18% per decade.) Even in the Arctic, where the immense empty landscapes promised only pristine air, scientists were startled to find a visible haze of pollutants drifting up from industrial regions. There was so much soot that some speculated it might alter the northern climate.

A very large old oak in the center - it has no terminal growth (young new leaf-bearing branches at the tip)

(I have seen it myself. Backpacking recently in the Sierra Nevada and the Canyonlands, decades after my first visits to these magnificent places, the views of distant cliffs and of the stars are never as sparkling clear as I was once used to seeing.)

New Worries

Talk of cooling from aerosols took a spectacular turn in 1983. A group of scientists, most of whom had already been studying aerosols, went public with warnings of an unexpected danger. If the blasts of a nuclear war injected smoke and dust into the atmosphere, a lethal "nuclear winter" might envelop the planet. The Russian meteorologist Kirill Kondratyev went on to point a finger at the nitrates (NOx) that had already been put into the atmosphere by weapons tests.

These had produced aerosols which, he surmised, might have been responsible for the decreased transparency of the atmosphere, and thus the cooling, observed during the 1960s. Only think how much cooling might follow a thousand nuclear explosions! Launching a nuclear strike would be literally suicidal, even if the other side never struck back. Other scientists disagreed, setting off a vehement public debate.

[First I've heard of NOx from nuclear explosions! For a fun diversion, there's a youtube video time-lapse dramatizing all the tests here.]

An even more horrendous effect of aerosols had been proposed back in 1980 by Walter and Luis Alvarez: the extinction of the dinosaurs when a giant meteor struck the Earth 65 million years ago. Calculations showed that dust from an asteroid impact could have fatally cooled the planet. All this was sharply contested by other scientists. The leading alternative that they developed to explain the doom of the dinosaurs was a series of gargantuan volcanic eruptions. That just showed another way that aerosols could change climate on an apocalyptic scale.

The "nuclear winter" and dinosaur extinction controversies contributed almost nothing to scientific study of ordinary climate change. But they encouraged a planetary-scale viewpoint, and sharpened awareness of the mortal fragility of the Earth's climate. Especially aroused was the aerosol community, or rather the scattering of researchers in diverse specialties who were gradually coalescing into a community. The furious controversies encouraged them to communicate with one another, and with meteorologists and other climate scientists.

Turning back to the way routine pollution might affect climate, scientists were slowly hacking a way through the jungle of complexities. A few meteorologists gradually worked out the implications of Twomey's studies, noticing how increasing emission of aerosols could create lingering misty clouds that might reflect enough sunlight to offset the warming expected from greenhouse gases. It was hard to know whether nature really acted according to these difficult calculations, and most experts paid little heed. After all, even massive direct cloud seeding had never been proven capable of doing much, despite decades of experiments. As Twomey admitted in 1980, "clear field verification has not been obtained" for various key predictions.

Finally in 1987 a dramatic visible demonstration convinced many scientists that the theory deserved respect. Satellite pictures of the oceans displayed persistent clouds reflecting sunlight above shipping lanes — a manifest response to ship-stack exhaust. Apparently aerosols could indeed create clouds, enough to outweigh the particles' direct interactions with radiation. (Later studies showed there were inconsistencies, as usual with aerosols. In some cases emissions from ships made for more cloudiness, in some cases less.) It was also becoming clear that humans were the dominant source of the atmosphere's sulfate aerosols. Nevertheless, many scientists continued to think of aerosols as "local" pollution and worried little about global implications.

The closer scientists got to definite answers, the more they noticed additional factors that they ought to figure in. For example, studies of the surprising dwindling of ozone over Antarctica (the "ozone hole") revealed in 1985 that crucial reactions took place on the surface of ice crystals floating high in the atmosphere. Scientists had dismissed surface reactions on particles as unlikely to make much difference for the chemical structure of the upper atmosphere. Now they saw the reactions were yet another set of complex problems that they would have to investigate.

Even more troublesome was the fact that any climate change would alter the natural background emission of aerosols. For example, if deserts expanded (whether from direct human activity or climate change) there would be more airborne dust. Meanwhile pollution studies showed that altering the amount of one type of aerosol in the air would start a chain of reactions that would alter the distribution of sizes and other key characteristics of other aerosols. And these subtle calculations themselves, one author warned, "do not do justice to the complexities of the real atmosphere."

On top of all that, there could be biological feedbacks. The most intriguing suggestion was that the nuclei for condensation of clouds in the pure air over the oceans might come primarily from dimethylsulfide (DMS) molecules, whose chief source was living plankton.It was another feedback dependent on temperature which might stabilize the climate — or might not. It would take decades of research to show, and even then only tentatively, that the effect was too small to make much difference.

Even if researchers set aside such issues, and even if they could resolve all the problems of cloud formation, they would still be far from knowing precisely how aerosols might affect climate. Few studies had even taken into account the fact that human activity emitted far more aerosols in some places than in others, so that the commonly used global averages could hardly represent the real situation. In some regions there would be too many particles to make normal clouds, in other regions too few. The properties of the aerosols themselves would be different in humid and dry regions. Yet climate scientists mostly continued to treat aerosols as a globally uniform background, mainly of natural origin. Atmospheric chemistry, observations of regional haze, and climate models were still such different fields that it was hard for any one person to assemble a coherent story.

Calculating Aerosol Effects (1990s - )

By 1990, scientists understood that human activity produced somewhere between a quarter and a half of all the aerosol particles in the lower atmosphere, including industrial soot and sulfates, smoke from debris burned when forests were cleared, and dust from semi-arid lands turned to agriculture or over-grazed. The consequences, if any, were entirely uncertain — "at this stage neither the sign nor magnitude of the proposed climatic feedback can be quantitatively estimated." Interest remained focused on greenhouse gases, which were expected to dominate climate change sooner or later.

Some scientists, however, did realize they had to take into account what the recent increase in aerosols meant for climate. Hansen called for better monitoring and more studies. Experts increasingly admitted that global climate change was not a matter of CO2 alone. It came from a variety of effects ("forcings") on incoming and outgoing radiation due to a variety of gases and aerosols. A leader in the work remarked that it was this shift of viewpoint — looking at changes in the energy balance rather than attempting to calculate surface temperature changes — that made meaningful global calculations possible. He added that the calculations "would not have been possible without an enormous amount of work measuring the actual properties of atmospheric aerosols."

Workers in the various fields that dealt with aerosols increasingly exchanged information and ground out observations and computations. Dramatic advances in laboratory instrumentation made it possible to measure microscopic particles one by one, providing context for a new wealth of sophisticated satellite observations. Specialists began to pin down the most important characteristics of aerosol particles, from the regions where different kinds were emitted to the ways they interacted chemically.

In the early 1990s, Charlson and others worked to persuade aerosol experts that sulfates could cause significant cooling, simply by scattering back incoming solar radiation. The effects of sulfate particles through stimulating cloudiness were harder to estimate, but appeared to add still more cooling. In a pioneering 1991 calculation, Charlson and his allies concluded that the scattering of radiation by humanity’s sulfate emissions was roughly counterbalancing the CO2greenhouse warming in the Northern Hemisphere. In retrospect, this was the key paper for establishing the net effect of aerosols on the planet's heat balance. The calculation, however, was admittedly full of uncertainties.

In 1991 Mount Pinatubo in the Philippines exploded. A mushroom cloud the size of Iowa burst into the stratosphere, where it deposited some 20 million tons of SO2, more than any other 20th-century eruption. Hansen's group saw an opportunity in this "natural experiment." It could provide a strict test of computer models. From their calculations they boldly predicted roughly half a degree of average global cooling, concentrated in the higher northern latitudes and lasting a couple of years. Exactly such a temporary cooling was in fact observed.

Human pollution of the atmosphere should do the same, for although black soot particles absorbed radiation and would bring some warming, the cooling from cloud formation and sulfates seemed likely to outweigh that. Most scientists now agreed that aerosols emitted by the "human volcano" had indeed acted like an ongoing Pinatubo eruption, offsetting some of the greenhouse warming.

Papers published in 1992 concluded that the smoke from slash-and-burn farming of tropical forests might have been enough all by itself to cancel a large share of the expected warming. Other scientists reported that the direct effect of sulfates blocking sunlight "completely offsets the greenhouse effect" in the most industrialized regions. Yet another team estimated that the indirect action of sulfates, making clouds darker, could have a still stronger cooling effect. As one expert remarked, "the fact that aerosols have been ignored means that projections may well be grossly in error." Thus efforts to restrict sulfate emissions, however important that might be for reducing acid rain and other unhealthy pollution, might hasten global warming.

Computer modelers returned to their simulations of global temperature, and found they could get curves that matched the observations since the 1860s quite closely provided they included increases in sulfate aerosols as well as CO2. The key paper, constructed at the Hadley Centre for Climate Prediction and Research in the United Kingdom, took a model that coupled the atmosphere and oceans and ran it through the centuries as the CO2 level rose, once without aerosols and once with them. The latter was clearly a better match to the actual historical record. Published in 1995, the result made a strong impression on scientists.

Because aerosol pollution was greater in some regions than others, whereas CO2 levels were about the same everywhere, modelers could even try to disentangle the two influences. To be sure, there was a risk that with aerosol effects poorly understood, the modelers might merely be adjusting their numbers until they reproduced the climate data, overlooking other possible factors. But the new results incorporating aerosols did give, for the first time ever, a plausible and consistent accounting of the main features of 20th-century climate.

In particular, it was now confirmed that industrial pollution had been a strong factor in the mid-century dip of Northern Hemisphere temperatures. As Bryson had speculated back in the 1970s, the effects of aerosol emissions from human industry were comparable to the effects of a large volcanic eruption. These results led directly to a 1995 announcement by the Intergovernmental Panel on Climate Change (IPCC) that human influence on climate had probably become "discernible." Scientists might have been convinced of global warming a decade or so earlier, but for their failure to grasp the cooling effect of aerosols.

The reprieve from warming would be temporary. As CO2 and other greenhouse gases inexorably accumulated in the atmosphere, they were overtaking the now nearly stable level of aerosol pollution. The IPCC's next report, issued in 2001, pointed out how industrialized nations were taking steps to reduce pollution. Considering various possibilities, the panel reported a high upper limit for where greenhouse warming might go during the 21st century: if the use of fossil fuels continued to expand at a breakneck pace while pollution controls restricted aerosols, global temperatures might shoot up nearly 6°C.

A minority of experts dissented from the panel's confidence that the improved computer models gave solid information. The critics warned that "given the present uncertainties in aerosol forcing, such improvement may only be fortuitous." To clear up the uncertainties, scientists needed better information not only on how aerosols interacted with weather, but also on just what kinds of aerosols human activity stirred up and just where the winds blew them. None of that was measured well enough.

The old discussion of whether pollution brought warming or cooling was still yielding surprises. In particular, evidence turned up that much more soot ("black carbon") was puffing into the air than had been suspected. For example, a team under Veerabhadran Ramanathan deploying ships, aircraft and balloons in the Indian Ocean in 1999 detected a huge drifting "brown cloud."

It was a miasma caused by human activity, expanded from the haze that Bryson had noticed while flying over India a third of a century earlier (it included diesel exhaust and smoke from stoves burning cow dung or charcoal as well as smoke from factories and fires to clear farmland). Hansen now drew attention to the warming potential of such pollutants. To be sure, the dark smokes shaded the surface and thus made for cooling. But higher in the atmosphere the soot absorbed radiation so thoroughly, according to his group's new calculations, that overall it added strongly to global warming — perhaps second only to CO2.

Cutting this sort of pollution could not only reduce damage to local and global climates, but also prevent hundreds of thousands of premature deaths from respiratory illnesses. Some scientists argued that before going all out to restrain greenhouse gases, the world should attack the rightly despised smokes, the most ancient form of technological pollution.

Later, beginning around 2002, climatologists were surprised by evidence that hazes were having an even bigger effect than they had supposed. As far back as 1989, Atsumu Ohmura in Switzerland had published evidence that sunlight had been growing dimmer globally throughout the 20th century. Like the other indications of widespread turbidity noted above, Ohmura’s work had attracted little attention, even though some computer modellers had begun to worry that their models did not seem to include enough aerosol absorption. Now evidence turned up by other scientists convinced many experts that the Northern Hemisphere, at least, had seen a dimming of 10 percent or more — much more than most experts had thought, indeed probably great enough to affect agriculture. Aerosol pollution was the only plausible cause. "There could be a big gorilla sitting on the dining table, and we didn't know about it," Ramanathan admitted in 2004.

Many aerosol specialists now suspected that they had badly underestimated how strongly greenhouse warming had been held back by the cooling effect of aerosols. That had given the world "a false sense of security" about global warming, the respected atmospheric scientist Paul Crutzen warned in 2003. For the "global dimming" trend was not really global but regional, and since the 1980s it had flattened out or even reversed in some regions. Nobody could be sure why, but a likely cause was the pollution controls that many industrialized nations were imposing, working effectively to reduce sulfates.

Europe, which had the strictest controls, was the main region where the sunlight was now significantly brighter. Dimming was still getting stronger over China and other developing nations, but these nations were laying plans to clean up their air. Some experts began to worry that eventually this would bring a "global brightening," so that temperatures would rise faster than the standard greenhouse warming calculations predicted. Whatever was happening, it was more obvious than ever that the world urgently needed better measurements of aerosols, and better models for how they blocked sunlight.

Large uncertainties also remained in figuring how aerosols interacted with gases, and above all with water vapor (the main "indirect effect”"or "Twomey effect"). Questions were raised once again by detailed observations that confirmed the speculation that had first started scientists worrying back in the 1960s — cirrus clouds grew from jet contrails. Indeed the clouds measurably influenced the climate in regions beneath heavily traveled air routes. Experts published widely divergent models for the formation of such clouds and their absorption of radiation. Controversial measurements published in 1995 claimed that clouds absorbed much more radiation than the conventional estimates said, raising a specter of "missing physics."

As one researcher complained, "The complexity of this problem seems to grow with each new study." It was reasonable to expect that improvements in theoretical models and measuring techniques would eventually lead to a reconciliation (indeed within the next decade theory and observations would largely converge). But the physics was so complex that Ramanathan admitted, "If I wake up with a nightmare, it is the indirect aerosol effect." And this effect was only one of several areas where new studies kept showing that, as Ramanathan and a colleague remarked, people were still "in the early stages of understanding the effects" of aerosols.

This persistent ignorance about aerosols — their direct and indirect effects, and even their concentrations — was the largest single obstacle to attempts to predict future climate, especially if you tried to drill down to predict for a given region. Funding agencies accordingly pushed vigorous and costly efforts to measure aerosol effects, and significant results accumulated in the early 21st century. Yet different computer models still gave substantially different results, and if some issues were settled, new puzzles appeared in theoretical papers or field studies to provoke new controversies — and more worries.

For example, in 2008 Ramanathan's group showed that black carbon aerosols had a much stronger warming effect than earlier calculations had estimated. Among other things, the calculations had not accounted for the combined effects of black carbon with sulfate aerosols. It was now plainer than ever that a simple policy of reducing these sooty emissions, everywhere from European diesel automobiles to East Asian cooking fires, would not only benefit public health but would help delay global warming.

What if there remained other significant factors that had been overlooked, for example in estimates of the effect of sulfate aerosols? A few experts had been worrying for years that sulfates might have been more effective in holding back warming than computer modelers had guessed so that as nations continued to reduce their sulfate emissions, global temperatures might leap upward. On the other hand, if the historical aerosol effects had been overestimated, then future temperatures might rise more gradually than expected.

Despite the uncertainties, most experts felt that they could at least fix a rough range for the gross global consequences. They grew increasingly certain that the sum of human aerosol emissions had a net cooling influence, at least in most parts of the world. Estimates of the magnitude of the cooling (both directly, and indirectly through clouds) ranged from fairly small to quite strong. Pollution was delaying the appearance of greenhouse warming in some industrialized regions and perhaps everywhere. As greenhouse gas emissions continued to accumulate, few doubted that a dangerous global warming would be unmasked, surging past any possible aerosol cooling effects.

THE END. This rock in the stream is just here because I like it.

And this infant skunk cabbage is here because it's nice to see something alive and growing.

I don't know if this particular fungus is bad for trees, but it's very pretty.

I can't decide which picture I like better.

So, here are all three.

This pair of trees is included to disprove the idiots who say trees are dying because they are too close together. Not only is one spilling over another, they were growing just fine for years in what is plainly rock-strewn soil.

Trees can live even when a good portion of their root system has been eroded away.

But once a canker starts, they don't have much time left.

This is a good place to talk about bark. I've recorded here and many other times that bark is splitting, cracking and falling off. That could be from internalized damage manifesting its way out, or fungus. But there might be another mysterious symptom, and every now and then I come across an example where it looks almost like bark is corroding from the surface. Someone carved a heart in this tree, and since that time, it looks like the bark has shriveled, desiccated.

This is the branch of a sycamore tree that has fallen to the ground fairly recently. It displays the characteristic mottling and peeling of the species that is so beautiful and distinctive.

Here is the main trunk of the tree from which it fell. This older bark is rough, coarse and, as shown by the brown spot in the center, falls off at the slightest touch.

The next two are beeches which are terrific examples because they show both conditions on the same trunk. Normally, beeches are elegant for their smooth bark, that looks like leather, slightly crinkled in places but not in any kind of section.

I have no idea what causes this but it is happening on every kind of tree. I wonder if the rain and fog are so acidic now, that it is actually caustic when it bathes the surface of the bark.

Mostly it happens so gradually and uniformly that people don't realize the bark has changed texture.

Beech and fruit trees are the best for spotting the transformation, maybe because they start out so smooth that it is more visible than with oaks, maples and other naturally coarser trunks.

I'm not sure what kind of tree this is, it produces some sort of nut. In the center you can see that the outer layer of deeply furrowed bark has broken off leaving a flat dent. Oak trees are doing this too.

The sun started to set so I hurried past trees lit up by its lowering rays.

It's hard to describe just how unremittingly the destruction of this fine old forest has transpired.

It was quite funny - getting back to our friend Cecil - to discover that even though he is probably a bona fide Tea Partier, we had some things in common, not least total cynicism about government, and a deep pessimism about the future.

The plunge of the global economy, let alone the debt-shackled US economy, is not reversible, if only because the corporatocracy will never willingly abdicate one shred of the power it has snatched, not without wars and the rise of blatant - as opposed to stealthy, consumerist - fascism.

More fundamentally, the economic disaster cannot improve because it is based not merely on the greed of the few, but upon far more basic, intractable and insolvable limitations to the exponential growth that has characterized the past 150 years or so. Although we could, theoretically, mitigate the effects temporarily, together these contraints amount to one colossal, converging catastrophe, particularly considering that any one of which in isolation would be enough to, sooner or later, end industrial civilization.

I think of it as the Trifucta - the unsustainable financial ponzi schem;, peak oil and other resources; and pollution causing climate change and ecosystem collapse.

But within each of those categories there are a whole series of lesser complications, each existential threats to at least a portion of humanity in their own right. Here's my list of favorites, in no particular order:

floods, droughts, violent weather and the disruption of seasonal relationships between species

ocean acidification

overfishing

crop failures, famine

peak oil

peak other resources - rare minerals, fertilizers and so forth

fresh water shortages from melted glaciers and over-use

sea level rise (nuclear power plants inundated)

methane release

habitat destruction leading to extinctions

overpopulation

loss of whatever shreds of the social safety net

closing of hospitals, jails and schools

rising crime, especially from power shortages

riots based on class and age, race and religion

wars between nations

massive, widespread psychological breakdowns as people can't cope with the losses

pandemics exacerbated by loss of power and no water for hygiene and no medicine

pollution. Especially pollution.

I think pretty much the entire scientific and activist community is making a mistake by pandering to the deniers. I posed the following question to a group of activists who were discussing a recent poll indicating that the more educated Republicans are, the more likely they are to be deniers, and got no response at all:

My experience with deniers is that the first response they have is, okay, if burning fuel is causing climate change, what are you going to replace it with? When they're told that it can be replaced with wind, solar, geothermal, hydro, nuclear, etc. they just don't believe it.

So, they get very suspicious of the entire enterprise, and throw the concept that we are changing the climate out the window completely, because they can't imagine life without their toys.

In this sense they are quite correct. If we are going to stop using dirty fuels to an extent that would slow climate change, it would require enormous reduction in lifestyle, particularly for westerners. Sacrifice. No more plane trips, for starters. No more giant tankers transporting global trade.

If the big green groups and prominent activists never start to be honest about the need to completely reinvent society organized around localized sustainable groups in a much simpler existence, I think we'll all - whether climate hawks or climate deniers - just be waiting for Mother Nature to do it for us.

There are many, many authors who are making quite the career out of declaring that civilization is on the brink of impending doom. And yet, they always have that little bit of hope at the end, that we will somehow relocalize food production in the midst of ravenous zombies who haven't a clue how to preserve food but do have weapons and ammo. John Michael Greer the "Archdruid", Lester Brown and Richard Heinberg come to mind. As a commenter on his last newsletter wrote: "We had a million years of collective homicide when the planet had ample resources, any idea that we can find a gentle altruistic middle ground now when we’re really running out of food is laughable, except that I don’t feel like laughing."

The orchard in the setting sun. There are wood chips left on the grass. Despite the constant effort to clear, chop
and chip, it's impossible to get away from trees and branches all over the ground, there are so many.

I got an email from Paul Gilding, who is the Australian author of "The Great Disruption" which although extremely well-written, I always thought would be better titled "The Great Convulsion" with all the uncontrolled violence that implies. But that notion doesn't sell books or get much applause, I suppose. The new message had a link to his recent TED talk, which is embedded below. He began with the concept "the Earth is full...We are living beyond our means".

So far, so good - but after that, it was disappointing.

One of the first absurdities was this: "Scientists like James Hansen tell us we may have to eliminate net CO2 emissions from the economy in just a few decades."

MAY have to? In a few decades? We'll be completely fried by then!

I did agree with this: "...eliminating net CO2 emissions from the economy in 20 years is actually pretty easy and pretty cheap...not very cheap but cheaper than a collapsing civilization..." but then he ruined it with the conclusion:

"We can transform our economy. We can do it with proven technology. We can do it at an affordable cost. We can do it with existing polical structures. The only thing we need to change is how we think and how we feel...We've built a powerful foundation of science, knowledge and technology - more than enough to build a society where nine billion people can live decent, meaningful and satisfying lives...The earth can support that if we choose the right path".

Wonderful photo journal and science rendering, even in the absence of essential reference to metal nanoparticle aerosols, or chemtrails.

Poor Paul Gilding quaintly finesses the orchestrated destruction of our society with the usual deceptions of faith, hope, and charity.

This destruction is no accident.

Poem – The Beast

The anger, The pain, The hurt, The stain,A cancerous tumor from within,Or a demonic spirit that possesses,Do I need surgery or an exorcism?It throbs from within,You feel the heat protrude,Your heart beats in rhythms,Skins tightens and crawls,You cannot talk,Do I need surgery or an exorcism?I must endure pain to release this beast,So I can taste freedom forever,Who gave me this gift,Society and my parents.